The present invention relates to the field of electroplating of metals and more particularly to novel electroplating baths, electroplating aqueous solutions and methods of electroplating copper onto a substrate.
Copper based materials are frequently used as low resistivity interconnects in the microelectronics industry. In addition to its use for IC interconnects, the use of copper electro-deposition to produce high aspect ratio structures such as vias, pillars, and bumps on semiconductor chips is one of the key technologies for 3D packaging. It is important that an electroplating process for copper be sufficiently fast to allow the processing of a large number of substrates and have an acceptable yield. This is particularly important for the production of the high aspect ratio structures that are needed for 3D packaging, since larger amounts of copper need to be plated for this purpose. However, current electroplating processes for copper are not sufficiently fast because the copper plating speed is normally limited by the mass transport of copper ions in the aqueous plating solution in the diffusion layer area. Only high copper ion concentrations are able to accommodate high speed plating under mass transport controlled conditions. However the copper concentration is limited by the solubility of copper salts at ambient temperature to allow the transportation of electrolytic solutions from material suppliers to manufacturers. Therefore, the maximum copper concentration is limited by the copper salt solubility in any selected electrolytic solution at normal transportation temperatures.